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626 H. UEDA, M. SHINODA AND H. KAMAHORI
pentad
1.5
0.0
-1.5
Snow-disappearance Pentads
66 67 68 69 70 71 72 73 74 75 76 77 78 79
year
anomaly (45-60N, 30-60E)
80 81 82 83 84 85 86 87 88 89 90
Figure 8. Year-to-year variations of snow-disappearance pentads anomalies for the EEP (45–60 °N, 30–60 °E)
Figure 9. Composite difference of snow boundary between late-disappearance years (1979, 1980, 1987) minus early disappearance years
(1975, 1983, 1990). Positive (negative) values mean slow (rapid) northward retreat of snow-cover extent
interesting feature in Figure 10 is that differences of surface temperature between the extreme years are
absent in February and early March, whereas they are much enhanced in mid winter and in late March and
April. This might suggest a periodicity of atmospheric circulation patterns across the continent that may
be associated with seasonal change of the so-called North Atlantic oscillation (Portis et al., 2001) or other
atmospheric teleconnection patterns.
In order to confirm the atmospheric conditions relevant to early snow-disappearance, we present the
composite differences of vertically integrated meridional advection during March and April (Figure 11). Larger
heating anomalies can be found to the northeast of the Black sea. This pattern resembles those found in the
horizontal (meridional plus zonal) advection (not shown) and wind fields (Figure 3(a) and (b)). These results
Copyright © 2003 Royal Meteorological Society Int. J. Climatol. 23: 615–629 (2003)